The present invention generally relates to video signal reproducing apparatuses, and more particularly to a video signal reproducing apparatus for producing a reproduced video signal from which a reproduced picture of a high quality can be obtained, by use of two reproduced video signals having a mutual time difference of approximately one field.
Generally, in a helical scan type magnetic recording and reproducing apparatus (hereinafter simply referred to as a video tape recorder or VTR), a video signal is recorded on a moving magnetic tape by one or a plurality of rotary magnetic heads and the recorded video signal is reproduced from the tape by the one or plurality of heads. An upper limit frequency of the video signal is 4.2 MHz, for example, and the frequency band of the video signal is wide. As is well known, in order to record the video signal having the wide frequency band on the tape by frequency-modulating the video signal, for example, and then reproduce the recorded signal from the tape, a relative speed between the head and the tape must be set to a high speed which is over a predetermined value. In addition, it is necessary to use a high performance head having a high sensitivity in a high frequency range.
However, in the case of the VTR for home use, the relative speed between the head and the tape is inevitably set to a speed which is considerably lower than the predetermined value because of the need to reduce the cost of the apparatus, downsize the apparatus, and reduce the weight of the apparatus. For this reason, the recording and reproducing frequency band becomes narrower than the original frequency band of the video signal, and it is impossible to produce a reproduced video signal from which a reproduced picture of a high quality can be obtained.
Accordingly, a video signal recording and reproducing apparatus was previously proposed in a U.S. patent application Ser. No. 620,016, now U.S. Pat. No. 4,682,250, entitled "VIDEO SIGNAL RECORDING AND REPRODUCING APPARATUS" filed June 13, 1984 in which the assignee is the same as the assignee of the present application. According to this previously proposed video signal recording and reproducing apparatus, a recording video signal is sampled at a frequency fs which is slightly higher than the frequency band of the recording video signal, and the sampled signal is recorded on a recording medium. The signal which is reproduced from the recording medium is delayed by one horizontal scanning period, and the delayed signal and an undelayed signal are alternately sampled with the frequency fs and mixed so as to obtain a reproduced video signal which has essentially been sampled at a frequency 2 fs which is twice the frequency fs. According to this previously proposed apparatus, it is possible to reproduce signal components in a relatively high frequency range, with a relatively narrow frequency band, and thus, it is possible to obtain a reproduced video signal having a wide frequency band. However, in a reproducing system of this previously proposed apparatus, a field memory is used to obtain two kinds of reproduced sampled signals having a mutual time difference of one field, and as a result, there are problems in that the apparatus becomes complex and expensive.
On the other hand, it is known from a Japanese Laid-Open Patent Application No. 58-77373, for example, that it is possible to obtain a flicker-free reproduced picture having a high picture quality by displaying a reproduced video signal as a progressively scanned frame of picture. According to this known reproducing apparatus, an input reproduced video signal is supplied to a first time base compression circuit and a field memory, and the first time base compression circuit supplies to a first terminal of a switching circuit a first time base compressed video signal which is obtained by time base compressing the input reproduced video signal by 1/2. The input reproduced video signal is a video signal which is to be displayed with an interlaced scanning in conformance with an existing television system. The input reproduced video signal which is delayed by one field in the field memory is time base compressed by 1/2 into a second time base compressed video signal in a second time base compression circuit. The second time base compressed video signal from the second time base compression circuit is supplied to a second terminal of the switching circuit. The switching circuit alternately passes the first and second time base compressed video signals respectively supplied to the first and second terminals thereof for every 1/2 the horizontal scanning period, and supplies to a monitoring display apparatus a reproduced video signal in which the first and second time base compressed video signals are alternately transmitted in time sequence. The monitoring display apparatus displays the reproduced video signal as a progressively scanned frame of picture. Hence, although a flicker is generated in the reproduced picture when reproducing with the interlaced scanning a picture which includes a pattern such as horizontal lines since it is only possible to carry out the reproduction in terms of frames according to the interlaced scanning, it is possible to carry out the reproduction in terms of fields according to this conventional reproducing apparatus and hence obtain a flicker-free reproduced picture of a high quality. However, this conventional reproducing apparatus also uses a field memory and there are problems in that the apparatus becomes complex and expensive.